To deploy manually, make sure the process definition is somewhere on your classpath. For example, I use $TOMCAT_HOME/webapps/alfresco/WEB-INF/classes/alfresco/extension/workflows. Then, go to the workflow console and type "deploy /alfresco/extension/workflows/someProcessDef.xml". Note that for those of you using Alfresco 4 the syntax changes a little bit. You have to include the name of the engine you are deploying to (jbpm or activiti).

You can also configure a Spring context file to deploy your workflows for you. If you want to see how to do that, check out my advanced workflows tutorial (1st edition for jBPM and Explorer, 2nd edition for Activiti and Share).